Wonderful story from Atlas Obscura.

The cyanometer, invented in the 18th century by the Swiss scientist Horace-Bénédict de Saussure, had one evanescent purpose: to measure the blueness of the sky.

In 1760, when he was 20 years old, Saussure traveled from his home in Geneva to the base of Mont Blanc, the highest mountain in the Alps. Saussure, a brilliant student from a wealthy family, had already finished his studies at the Academy of Geneva, where he would soon be made a professor, at just 22 years old.

But at this moment he was free to explore, and he was captivated by the mountain, which had never been climbed—not all the way to its top, 15,774 feet above sea level. The young scientist dreamed of standing at the summit, and he offered a generous reward, of an unspecified amount, to the first person who reached it.

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